Objects are seen in three dimensions because light reflects from them and generates a light field in space. The two eyes of a viewer perceive this light field differently due to their different locations in space relative to the object, and the brain of the viewer processes the different perceptions of the light field by the two eyes to generate three-dimensional perception. If a second light field (LF′) is recreated that is the same as a first, original light field (LF), the viewer of LF′ will see the same object image in three dimensions. The basic quality of any three-dimensional imaging system therefore depends on the magnitude of the difference between LF and LF′, i.e., how close the imaging system can come to recreating LF.
Stereoscopic imaging is one well-known technique that simulates three-dimensional (“3-D”) images to humans by providing differing images of the same object or scene to the left and right eyes of the viewer. The principles of stereoscopic imaging have been applied to various areas for many years, including to the training of professionals, such as pilots to physicians, and to entertainment, such as 3-D movies and computer games. All of these systems rely upon segregating images for the right and left eyes. For example, an apparatus which sequentially displays different views to the left and right eye of a viewer has been used successfully in cartographic and other applications. In this instance, using stereo image alternation, a different view is sequentially presented to the left and right eye of the viewer. Stereographic effects have also been created by using cathode ray tubes or liquid crystal displays whereby a viewer wears special glasses such as polarizing glasses or liquid crystal shutter glasses in order to see a different image in the left and right eye. Stereoscopic imaging systems have suffered from an inability to allow multiple image views or aspects to a single viewer and to multiple viewers without expensive or cumbersome specialized eye gear or goggles.
Lenticular lenses and screens are one common technological approach that has been used to allow a viewer to see a left eye and right eye image separately without the need for specialized eye gear. For example, U.S. Pat. No. 5,838,494 to Araki describes a lenticular screen system that displays a plurality of striped images behind a corresponding lenticular screen or striped barrier such that a viewer sees with each particular eye only the image stripes that correspond to the appropriate parallax view for the left or right eye when the user is looking through the lenticular screen. Inherently, such lenticular lens and screen systems like this apparatus present only a limited number of different or varying image views to a viewer as the lenticular lens is placed between the viewer and the image and inherently limits the amount of image information that can reach the viewer's eyes. One screen, or plane, contains all of the information about the image or images while the other screen (or mask), placed between the imaging screen and viewer, contains only the lenticular lens or running slits that isolates the left eye image from the right eye image for the viewer. Whenever a viewer uses a parallax barrier-type of 3-D viewing system, the viewer is actually seeing the parallax barrier or the lenticular lens. The viewer is therefore unable to change position freely to “look around” the object image or change perspective as the viewer could in real life.
Various modifications have been made to the standard stereoscopic display systems in order to improve image quality and improve utility of the systems. For example, U.S. Pat. No. 5,930,037, issued to Imai, describes a lenticular lens stereoscopic image system that has mechanisms to prevent inverse stereoscopic viewing (when the right eye sees the image that is destined for the left eye and vice versa). While this invention addresses the particular problem of inverse stereoscopic viewing, this invention does not solve the problem of limited image views and aspects.
Similarly, U.S. Pat. No. 5,712,732, issued to Street, describes an improvement upon the lenticular screen system that provides a mechanism that electronically solves the problem that, when a lenticular lens is used, a viewer must be at a particular distance from and orientation to the lens in order for the lens to operate correctly. This invention comprises an automated measuring apparatus allowing a 3-D imaging system to determine the position of the viewer's head in terms of distance and position (e.g., left-right) relative to the screen. In this fashion an appropriate stereographic image pair can be presented to the user at any particular location. Again this invention relies upon a lenticular screen to separate the parallax views for the left and right eye of the viewer. The head location apparatus dictates various other geometries associated with viewing the stereographic pairs of an image. However, while this invention relates to adapting for the location of the viewer's head during parallax image viewing, it does not provide an ability to increase the number of aspects of an image that can be created and viewed, nor does it provide an ability to provide such multi-aspect images to multiple viewers simultaneously.
It would be desirable to have a 3-D imaging system that provides numerous aspects, perspectives or views to a given user or multiple users in a dynamic manner. It would further be useful for such viewing to take place in a flexible way so that the viewer is not constrained in terms of the location of the viewer's head when seeing the stereo image.